System and method for controlling tracking and seeking in an optical disc drive

ABSTRACT

A control system for controlling tracking and seeking in an optical disc drive for optical media with a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The control system determines whether an optical pickup unit is over the premastered or the writeable areas of the optical media by measuring peak to peak amplitude of a tracking error signal. Gains and calibration values are selected based on whether an optical pickup unit is over the premastered or the writeable areas of the optical media. Reading from and writing to the optical media is disabled while jumping tracks. Control of jumping tracks on the optical media includes controlling: jumping a single track on the optical media; jumping a specified number of tracks every specified number of revolutions of the optical media; auto jumpbacks, and jumping in forward or reverse directions. Parameters for controlling jumps include at least one of: jump type, number of tracks to jump, time delay between track jumps, number of revolutions of the optical media between jumps, and whether it is not safe to read from or write to the optical media. The control system performs long seeks by predicting whether the tracking actuator arm will be positioned over the premastered area or the writeable area at the end of the long seek, and to load calibration parameters corresponding to the type of media over which the tracking actuator arm will be positioned at the end of the long seek.

CROSS-REFERENCE TO CO-FILED APPLICATIONS

The present disclosure was co-filed with the following sets ofdisclosures: the “Tracking and Focus Servo System” disclosures, the“Servo System Calibration” disclosures, the “Spin Motor Servo System”disclosures, and the “System Architecture” disclosures; each of whichwas filed on the same date and assigned to the same assignee as thepresent disclosure, and are incorporated by reference herein in theirentirety. The Tracking and Focus Servo System disclosures include U.S.Disclosure Ser. Nos, 09/950,329, 09/950,408, 09/950,444, 09/950,394,09/950,413, 09/950,397, 09/950,914, 09/950,410, 09/950,441, 09/950,373,09/950,425, 09/950,414, 09/950,378, 09/950,513, 09/950,331, 09/950,395,09/950,376, 09/950,393, 09/950,432, 09/950,379, 09/950,515, 09/950,411,09/950,412, 09/950,361, 09/950,540, and 09/950,519. The Servo SystemCalibration disclosures include U.S. Disclosure Ser. Nos. 09/950,398,09/950,396, 09/950,360, 09/950,372, 09/950,541, 09/950,409, 09/950,520,09/950,377, 09/950,367, 09/950,512, 09/950,415, 09/950,548, 09/950,392,and 09/950,514. The Spin Motor Servo System disclosures include U.S.Disclosure Ser. Nos. 09/951,108, 09/951,869, 09/951,330, 09/951,930,09/951,328, 09/951,325 and 09/951,475. The System Architecturedisclosures include U.S. Disclosure Ser. Nos. 09/951,947, 09/951,340,09/951,339, 09/951,469, 09/951,337, 09/951,329, 09/951,332, 09/951,850,09/951,333, 09/951,331, 09/951,156 and 09/951,940.

The present disclosure was also co-filed with the following disclosuresU.S. patent Disclosure Ser. Nos. 09/950,516, and 09/950,365, each ofwhich was filed on the same date and assigned to the same assignee asthe present disclosure, and are incorporated by reference herein intheir entirety.

CROSS-REFERENCE TO CD-ROM APPENDIX

CD-ROM Appendix A, which is a part of the present disclosure, is aCD-ROM appendix consisting of 22 text files. CD-ROM Appendix A includesa software program executable on a controller as described below. Thetotal number of compact disks including duplicates is two. Appendix B,which is part of the present specification, contains a list of the filescontained on the compact disk. The attached CD-ROM Appendix A isformatted for an IBM-PC operating a Windows operating system.

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever.

These and other embodiments are further discussed below.

BACKGROUND

There is an ever increasing need for data storage devices having greaterstorage capacity with smaller form factors for multimedia systemsutilizing text, video, and audio information. Further, there is a largedemand for highly portable, rugged, and robust systems for use asmultimedia entertainment, storage systems for PDAs, cell phones,electronic books, and other systems. One of the more promisingtechnologies for rugged, removable, and portable data storage is WORM(write once read many) optical disk drives.

One of the important factors affecting design of an optical system (suchas that utilized in a WORM drive) is the optical components utilized inthe system and the control of actuators utilized to control the opticalsystem on the disk. The optical system typically includes a laser orother optical source, focusing lenses, reflectors, optical detectors,and other components. Although a wide variety of systems have been usedor proposed, typical previous systems have used optical components thatwere sufficiently large and/or massive that functions such as focusand/or tracking were performed by moving components of the opticalsystem.

Many early optical disks and other optical storage systems providedrelatively large format read/write devices including, for example,devices for use in connection with 12 inch (or larger) diameter disks.As optical storage technologies have developed, however, there has beenincreasing attention toward providing feasible and practical systemswhich are relatively smaller in size. Generally, a practical read/writedevice must accommodate numerous items within its form factor, includingthe media, media cartridge (if any), media spin motor, power supplyand/or conditioning, signal processing, focus, tracking or other servoelectronics, and components associated or affecting the laser or lightbeam optics. Accordingly, in order to facilitate a relatively smallform-factor, an optical head occupying small volume is desirable. Inparticular, it is desirable for a small optical head in the directionperpendicular to the surface of the spinning media.

Additionally, a smaller, more compact, optical head provides numerousspecific problems for electronics designed to control the position andfocus of the optical head including: the need for extensive drivecalibration and periodic drive recalibration, time critical servo statemachines to compensate for the flexible focus and tracking actuators,nonlinear and cross-coupled tracking and focus position sensors, dynamiccrosscoupling between the multiple servo loops, need for low powerconsumption to conserve battery life, removable and interchangeablemedia, robust handling of media defects, presence of both pre-masteredand user writeable areas on the same disk, need to operate in wide rangeof conditions including various physical orientations, wide range ofambient temperatures and humidity levels, and the presence of shock andvibration.

Therefore, there is a need for an optical head with a small form factorand, in addition, a servo system for controlling the head so that datacan be reliably read from and written to the optical media.

SUMMARY

A system, method, and apparatus in accordance with the present inventionincludes a code architecture that addresses the design challenges forthe small form factor optical head. Embodiments of a system and devicein accordance with the present invention utilize several unique methodsincluding sharing a general purpose processor between the servo systemand other drive systems in the device, using a dedicated high speedprocessor for time critical servo functions, communicating between thededicated servo processor and the shared general purpose processor,distributing the servo processing between the general purpose processorand the dedicated servo processor, and distributing the servo processingwithin the general purpose processor between a main loop process and abackground periodic event process.

In one embodiment, a control system for controlling tracking and seekingin an optical disc drive for optical media with a pitted premasteredarea that cannot be overwritten and a grooved user-writeable area thatcan be overwritten, includes instructions to determine whether anoptical pickup unit is over the premastered or the writeable areas ofthe optical media.

One aspect of this embodiment includes instructions operable to controltransition from a tracking idle state to a tracking turn on state when atracking turn on servo command is received. A tracking illegal state isentered if focus is not active.

Another aspect of this embodiment includes instructions operable to turntracking on and off and to control jumping tracks on the optical media.The instructions operable to control jumping tracks on the optical mediaare operable to control at least one of: jumping a single track on theoptical media; jumping a specified number of tracks every specifiednumber of revolutions of the optical media; auto jumpbacks, and jumpingin forward or reverse directions. Parameters for controlling jumpsinclude at least one of: jump type, number of tracks to jump, time delaybetween track jumps, number of revolutions of the optical media betweenjumps, and whether it is not safe to read from or write to the opticalmedia.

Another aspect of this embodiment includes instructions operable toselect gain and calibration values based on whether an optical pickupunit is over the premastered or the writeable areas of the opticalmedia. The instructions measure the peak to peak amplitude of a trackingerror signal when determining whether the optical pickup unit is overthe premastered or the writeable areas of the optical media and todisable reading from and writing to the optical media while jumpingtracks.

Another aspect of this embodiment includes instructions operable todelay transition to a tracking active state to allow time for controlsystem parameters to be initialized.

Another aspect of this embodiment includes instructions operable todetermine the status of the tracking functions and to generate a statusindicator of whether a track jump was successful, wherein the statusindicates at least one of: bad track, bad jump, good track, and goodjump.

Another aspect of this embodiment includes instructions operable togenerate a bias value for a tracking arm actuator, wherein the biasvalue can be used to provide a low frequency tracking control effort(TCE) and to handle high frequency TCE.

Another aspect of this embodiment includes instructions operable toperform long seeks. The instructions predict whether a tracking actuatorarm will be positioned over the premastered area or the writeable areaat the end of the long seek, and load calibration parameterscorresponding to the type of media over which the tracking actuator armwill be positioned at the end of the long seek, can be included. Thecontrol system waits until a time period allotted for performing thelong seek expires, and sets a bad seek indicator to indicate whether thelong seek failed or completed.

In another embodiment, a method for controlling tracking and seeking inan optical disc drive for optical media with a pitted premastered areathat cannot be overwritten and a grooved user-writeable area that can beoverwritten, comprises: turning tracking on and off; and jumping trackson the optical media.

Jumping tracks on the optical media includes controlling at least oneof: jumping a single track on the optical media; jumping a specifiednumber of tracks every specified number of revolutions of the opticalmedia; auto jumpbacks, and jumping in forward or reverse directions.Parameters for controlling jumps include at least one of: jump type,number of tracks to jump, time delay between track jumps, number ofrevolutions of the optical media between jumps, and whether it is notsafe to read from or write to the optical media.

Another aspect of this embodiment includes determining the status of thetracking functions and generating a status indicator of whether a trackjump was successful.

Another aspect of this embodiment includes selecting gain andcalibration values based on whether an optical pickup unit is over thepremastered or the writeable areas of the optical media. Theinstructions measure the peak to peak amplitude of a tracking errorsignal when determining whether the optical pickup unit is over thepremastered or the writeable areas of the optical media and to disablereading from and writing to the optical media while jumping tracks.

Another aspect of this embodiment includes generating a bias value for atracking arm actuator, wherein the bias value can be used to provide alow frequency tracking control effort (TCE) and to handle high frequencyTCE.

Another aspect of this embodiment includes performing long seeks bypredicting whether a tracking actuator arm will be positioned over thepremastered area or the writeable area at the end of the long seek, andto load calibration parameters corresponding to the type of media overwhich the tracking actuator arm will be posititioned at the end of thelong seek.

The methods in accordance with the present invention can be embodied inthe form of computer-implemented processes and apparatuses forpracticing those processes. The methods can also be embodied in the formof computer program code embodied in tangible media, such as floppydiskettes, CD-ROMS, hard drives, or any other computer-readable storagemedium where, when the computer program code is loaded into and executedby a computer, the computer becomes an apparatus for practicing theinvention. The method can also be embodied in the form of computerprogram code, for example, whether stored in a storage medium, loadedinto and/or executed by a computer, or transmitted over sometransmission medium, such as over electrical wiring or cabling, throughfiber optics, or via electromagnetic radiation, wherein, when thecomputer program code is loaded into and executed by a computer, thecomputer becomes an apparatus for practicing the invention. Whenimplemented on a general-purpose microprocessor, the computer programcode segments configure the microprocessor to create specific logiccircuits.

The above as well as additional objectives, features, and advantages ofembodiments of the present invention will become apparent in thefollowing detailed written description.

SHORT DESCRIPTION OF THE FIGURES

FIG. 1 a shows an optical drive with which various embodiments of a discdrive control system in accordance with the present invention may beutilized.

FIG. 1 b shows a diagram for an optical media that may be utilized inthe disc drive shown in FIG. 1.

FIG. 2 a shows an embodiment of an optical pickup unit mounted on anactuator arm that can be utilized with the optical drive shown in FIG.1.

FIGS. 2 b shows an embodiment of the optical pick-up unit that can beutilized with the optical drive shown in FIG. 1.

FIG. 2 c illustrates the optical path through the optical head of FIG. 2b.

FIG. 2 d shows an embodiment of optical detector positioning of theoptical pick-up of FIG. 2 b.

FIG. 3 is a block diagram of components for processing signals in a discdrive control system in accordance with the present invention.

FIGS. 3 a through 3 g show examples of mailbox messages that can becommunicated between components shown in FIG. 3 in accordance with thepresent invention.

FIG. 4 is a block diagram of components included in the signalprocessing system shown in FIG. 3.

FIGS. 4 a through 4 p show examples of servo commands that can beimplemented in the signal processing system shown in FIGS. 3 and 4.

FIG. 5 shows a block diagram of an embodiment of the servo thread shownin FIG. 4.

FIG. 6 shows a block diagram of an embodiment of the command handlershown in FIG. 5.

FIG. 7 shows a block diagram of an embodiment of the event handler shownin FIG. 5.

FIG. 8 shows a block diagram of an embodiment of the performance eventhandler shown in FIG. 5.

FIG. 8 a shows a block diagram of an embodiment of the servorecalibration process as shown in FIG. 8.

FIG. 9 shows a block diagram of an embodiment of the heartbeat interruptshown in FIG. 4.

FIG. 10 shows a block diagram of an embodiment of the power mode controlstate machine shown in FIG. 9. FIG. 11 shows a block diagram of anembodiment of the recovery manager shown in FIG. 9.

FIG. 11 a shows a diagram of an embodiment of a recovery state machinefor the recovery manager shown in FIG. 11.

FIG. 12 a shows a diagram of an embodiment of an off format detectionmanager that is executed as part of the classify problem state 1106′ inFIG. 11 a.

FIG. 12 b shows a diagram of components utilized to perform off formatdetection for the off format detection manager shown in FIG. 12 a.

FIG. 12 c shows a diagram of an embodiment of logic to perform offformat detection for the off format detection manager shown in FIG. 12a.

FIGS. 13 a, 13 b, and 13 c show diagrams of aspects of thetracking/seeking control state machine shown in FIG. 9.

FIGS. 14 a, 14 b, and 14 c show diagrams of aspects of the focus controlstate machine shown in FIG. 9.

FIG. 15 shows a diagram of an embodiment of the spin control statemachine shown in FIG. 9.

FIG. 16 shows a diagram of an embodiment of the physical sector addressstate machine shown in FIG. 9.

FIG. 17 shows a diagram of an embodiment of the laser control statemachine shown in FIG. 9.

FIG. 18 shows a diagram of an embodiment of the adjust gains statemachine shown in FIG. 9.

FIG. 19 shows a diagram of an embodiment of the continuous performancemonitor state machine shown in FIG. 9.

FIG. 20 a shows a diagram of logic included in an embodiment of the DSPstatus mailbox interrupt handler shown in FIG. 4.

FIG. 20 b shows a diagram of logic included in an embodiment of amailbox interrupt service routine that can be included in the DSP statusmailbox interrupt handler shown in FIG. 20 a.

FIG. 20 c shows a diagram of additional logic included in an embodimentof a mailbox interrupt service routine that can be included in the DSPstatus mailbox interrupt handler shown in FIG. 20 a.

DETAILED DESCRIPTION

Optical Disk Drive Overview

FIG. 1 a shows an optical drive 100 in accordance with the presentinvention. Optical drive 100 includes a spin motor 101 (called spindledriver on FIG. 1) on which an optical media 102 is mounted. Drive 100further includes an optical pick-up unit (OPU) 103 mechanicallycontrolled by an actuator arm 104. OPU 103 includes a light sourceelectrically controlled by laser driver 105. OPU 103 further includesoptical detectors providing signals for controller 106. Controller 106can control the rotational speed of optical media 102 by controllingspin motor 101, the position and orientation of OPU 103 through actuatorarm 104, and the optical power of the light source in OPU 103 bycontrolling laser driver 105.

Controller 106 includes R/W processing 110, servo system 120, andinterface 130. R/W processing 110 controls the reading of data fromoptical media 102 and the writing of data to optical media 102. R/Wprocessing 110 outputs data to a host (not shown) through interface 130.Servo system 120 controls the speed of spin motor 101, the position ofOPU 103, and the laser power in response to signals from R/W processing110. Further, servo system 120 insures that the operating parameters(e.g., focus, tracking, and spin motor speed) are controlled in orderthat data can be read from or written to optical media 102.

Optical media 102 can include pre-mastered portions and writeableportions. Premastered portions, for example, can be written at the timeof manufacture to include content provided by a content provider. Thecontent for example, can include audio data, video data text data, orany other data that can be provided with optical media 102. Thewriteable portion of optical media 102 can be written onto by drive 100to provide data for future utilization of optical media 102. The user,for example, may write notes or other information on the disk. Drive100, for example, may write calibration data or other operating data tothe disk for future operation of drive 100 with optical media 102. Anexample of optical media 102 is described in U.S. application Ser. No.09/560,781 for “Miniature Optical Recording Disk”, herein incorporatedby reference in its entirety. The R/W Data Processing 110 can operatewith many different disk formats. One example of a disk format isprovided in U.S. application Ser. No. 09/527,982, for “CombinationMastered and Writeable Medium and Use in Electronic Book InternetAppliance,” herein incorporated by reference in its entirety. Otherexamples of disk data fonnats are provided in U.S. application Ser. No.09/539,841, “File System Management Method;” U.S. application Ser. No.09/583,448, “Disk Format for Writeable Mastered Media;” U.S. applicationSer. No. 09/542,681, “Structure and Method for Storing Data on OpticalDisks;” U.S. application Ser. No. 09/542,510 for “Embedded DataEncryption Means;” U.S. application Ser. No. 09/583,133 for “Read WriteFile System Emulation;” and U.S. application Ser. No. 09/583,452 for“Storage Device With Embedded Encryption Means,” each of which is herebyincorporated by reference in its entirety.

Drive 100 can be included in any host, for example personal electronicdevices. Examples of hosts that may include drive 100 are furtherdescribed in U.S. patent application Ser. No. 09/315,398 for RemovableOptical Storage Device and System, herein incorporated by reference inits entirety. In some embodiments, drive 100 can have a relatively smallform factor such as about 10.5 mm height, 50 mm width and 40 mm depth.

FIG. 1 b shows an example of optical media 102. Optical media 106 caninclude any combinations of pre-mastered portions 150 and writeableportions 151. Premastered portions 150, for example, can be written atthe time of manufacture to include content provided by a contentprovider. The content, for example, can include audio data, video data,text data, or any other data that can be provided with optical media102. Writeable portion 151 of optical media 102 can be written onto bydrive 100 to provide data for future utilization of optical media 102.The user, for example, may write notes, keep interactive status (e.g.for games or interactive books) or other information on the disk. Drive100, for example, may write calibration data or other operating data tothe disk for future operations of drive 100 with optical media 102. Insome embodiments, optical media 102 includes an inner region 153 closeto spindle access 152. A bar code can be written on a portion of aninner region 153. The readable portion of optical media 102 starts atthe boundary of region 151 in FIG. 1 b. In some embodiments, writeableportion 151 may be at the outer diameter rather than the inner diameter.In some embodiments of optical media 102, an unusable outer region 154can also be included.

The pre-mastered portions 150 of the optical media 102 can have adifferent data density compared to the writeable portions 151. Dataprocessors in disc drive 100 can therefore use different clock ratesdepending on whether the pre-mastered portions 150 or the writeableportions 151 are being accessed. Disc drive 100 must also be able toread and write data at variable density. Further, each time a newcartridge containing the optical media 102 is inserted, drive 100 mustdetermine if different densities are included on the optical media 102,and adjust drive parameters if the data densities are different from theoptical media 102 previously used.

FIG. 2 a shows an embodiment of actuator arm 104 with OPU 103 mounted onone end. Actuator arm 104 in FIG. 2 a includes a pin 200 which providesa rotational pivot about axis 203 for actuator arm 104. Actuator 201,which in some embodiments can be a magnetic coil positioned over apermanent magnet, can be provided with a current to provide a rotationalmotion about axis 203. Actuator arm 104 further includes a flex axis204. A motion of OPU 103 substantially perpendicular to the rotationalmotion about axis 203 can be provided by activating actuator coil 206.In some embodiments, actuators 206 and 201 can be voice coils.

FIGS. 2 b and 2 c show an embodiment of OPU 103. OPU 103 of FIG. 2 bincludes a periscope 210 having reflecting surfaces 211, 212, and 213.Periscope 210 is mounted on a transparent optical block 214. Object lens223 is positioned on spacers 221 and mounted onto quarter wave plate(QWP) 222 which is mounted on periscope 210. Periscope 210 is, in turn,mounted onto turning mirror 216 and spacer 224, which are mounted on asilicon submount 215. A laser 218 is mounted on a laser mount 217 andpositioned on silicon submount 215. Further, detectors 225 and 226 arepositioned and mounted on silicon substrate 215. In some embodiments, ahigh frequency oscillator (HFO) 219 can be mounted next to laser 218 onsilicon submount 215 to provide modulation for the laser beam output oflaser 218.

Laser 218 produces an optical beam 224 which is reflected intotransparent block 210 by turning mirror 216. Beam 224 is then reflectedby reflection surfaces 212 and 213 into lens 223 and onto optical medium102 (see FIG. 1). In some embodiments, reflection surfaces 212 and 213can be polarization dependent and can be tuned to reflect substantiallyall of the light from laser 218. QWP 222 rotates the polarization oflaser beam 224.

The reflected beam 230 from optical medium 102 is collected by lens 223and focused into periscope 210. A portion (in some embodiments about50%) of reflected beam 230 passes through reflecting surface 213 and isdirected onto optical detector 226. Further, a portion of reflected beam230 passes through reflecting surface 212 and is reflected onto detector225 by reflecting surface 211. Because of the difference in pathdistance between the positions of detectors 225 and 226, detector 226 ispositioned before the focal point of lens 223 and detector 225 ispositioned after the focal point of lens 223, as is shown in the opticalray diagram of FIG. 2 c.

FIG. 2 d shows an embodiment of detectors 225 and 226 in accordance withthe present invention. Detector 225 includes an array of opticaldetectors 231, 232, and 233 positioned on a mount 215. Each individualdetector, detectors 231, 232, and 233, is electrically coupled toprovide signals A, E and C to controller 106. Detector 226 also includesan array of detectors, detectors 234, 235 and 236, which provide signalsB, F, and D, respectively, to controller 106. In some embodiments,center detectors 232 and 235, providing signals E and F, respectively,are arranged to approximately optically align with the tracks of opticalmedia 102 as actuator arm 104 is rotated across optical media 102.

The degree of focus, then, can be determined by measuring the differencebetween the sum of signals A and C and the center signal E of detector225 and the difference between the sum of signals B and D and the centersignal F of detector 226. A tracking monitor can be provided bymonitoring the difference between signals A and C of detector 225 andthe difference between signals B and D of detector 226. Embodiments ofOPU 103 are further described in application Ser. No. 09/540,657 for“Low Profile Optical Head,” herein incorporated by reference in itsentirety.

Embodiments of drive 100 (FIG. 1) present a multitude of control systemchallenges over conventional optical disk drive systems. A conventionaloptical disk drive system, for example, performs a two-stage trackingoperation by moving the optics and focusing lens radially across thedisk on a track and performs a two-stage focusing operation by moving afocusing lens relative to the disk. Actuators 201 and 206 of actuatorarm 104 provide a single stage of operation which, nonetheless in someembodiments, performs with the same performance as conventional driveswith conventional optical media. Further, conventional optical diskdrive systems are much larger than some embodiments of drive 100. Somemajor differences include the actuator positioning of actuator arm 104,which operates in a rotary fashion around spindle 200 for tracking andwith a flexure action around axis 204 for focus. Further, the speed ofrotation of spindle driver 101 is dependent on the track position ofactuator arm 104. Additionally, the characteristics of signals AR, BR,CR, DR, ER, and FR received from OPU 103 differ with respect to whetherOPU 103 is positioned over a pre-mastered portion of optical media 102or a writeable portion of optical media 102. Finally, signals AR, BR,CR, DR, ER, and FR may differ between a read operation and a writeoperation.

It may generally be expected that moving to a light-weight structuraldesign from the heavier and bulkier conventional designs, such as isillustrated with actuator arm 104, for example, may reduce many problemsinvolving structural resonances. Typically, mechanical resonances scalewith size so that the resonant frequency increases when the size isdecreased. Further, focus actuation and tracking actuation in actuatorarm 104 are more strongly cross-coupled in actuator arm 104, whereas inconventional designs the actuator and tracking actuation is moreorthogonal and therefore more decoupled. Further, since all of theoptics in drive 100 are concentrated at OPU 103, a larger amount ofoptical cross-coupling between tracking and focus measurements can beexperienced. Therefore, servo system 120 has to push the bandwidth ofthe servo system as hard as possible so that no mechanical resonances inactuator arm 104 are excited while not responding erroneously tomechanical and optical cross couplings. Furthermore, due to the loweredbandwidth available in drive 100, non-linearities in system response canbe more severe. Further, since drive 100 and optical media 102 aresmaller and less structurally exact, variations in operation betweendrives and between various different optical media can complicatecontrol operations on drive 100.

One of the major challenges faced by servo system 120 of control system106, then, include operating at lower bandwidth with large amounts ofcross coupling and nonlinear system responses from operating closer tothe bandwidth, and significant variation between optical media andbetween different optical drives. Additionally, the performance of drive100 should match or exceed that of conventional CD or DVD drives interms of track densities and data densities. Additionally, drive 100needs to maintain compatibility with other similar drives so thatoptical media 102 can be removed from drive 100 and read or written toby another similar drive.

Most conventional servo systems are analog servos. In an analogenvironment, the servo system is limited with the constraints of analogcalculations. Control system 106, however, can include substantially adigital servo system. In contrast to an analog servo, in a digital servoa processor such as a digital signal processor calculates the focus andtracking error signals (FES and TES) directly from digitized opticalsensor signals. A digital servo system, such as servo system 120, thushas a higher capability in executing solutions to problems of systemcontrol. A full digital servo system is limited only by the designer'sability to write code and in the memory storage available in which tostore data and code. Embodiments of servo system 120, then, can operatein the harsher control environment presented by disk drive 100 and arecapable of higher versatility towards upgrading servo system 120 and forrefinement of servo system 120 compared to conventional systems.

Further requirements for drive 100 include error recovery procedures.Embodiments of drive 100 which have a small form factor can be utilizedin portable packages and are therefore subject to severe mechanicalshocks and temperature changes, all of which affect the ability toextract data (e.g., music data) from optical media 102 reliably or, insome cases, write reliably to optical media 102. Overall error recoveryand control system 106 is discussed below, while tracking, focus, seek,and calibration processes are discussed in the application entitled“Tracking, Focus, and Seek Functions with Calibration Processes in aServo System for an Optical Disk Drive”.

Control System Signal Processing Overview

Referring now to FIG. 3, a block diagram of components included in asystem for processing signals in a disc drive control system is shownincluding processor 302, digital signal processor (DSP) 304, and mailbox306. Processor 302 performs diagnostic and other non-time criticalfunctions, while DSP 304 performs functions that are time critical.Processor 302 and DSP 304 can be co-located on the same chip and, in oneembodiment, can communicate via mailbox 306. In other embodiments,processor 302 and DSP 304 can communicate via other suitable means suchas a data bus, serial interface, or shared, dual-ported memory. STMicroelectronics model number 34-00003-03 is an example of amicroprocessor chip that is suitable for use as processor 302 and DSP304.

DSP 304 can be slaved to processor 302, which performs overall controlfunctions along with calibration and error recovery functions. DSP 304includes instructions for controlling the focus and tracking at a veryhigh sample speed, and it also generates high order compensationsignals. Processor 302 takes over control when errors are detected andcomponents in the servo system 120 (FIG. 1 a) need to be adjusted oroperation is to be discontinued. Processor 302 issues commands to DSP304 via mailbox 306, and DSP 304 uses mailbox 306 to provide informationto processor 302 regarding how well it is performing the requestedfunctions.

In one embodiment, processor 302 receives defect signal 308, spinvelocity signal 310, and angular spin speed signal 312, and outputs spincontrol signal 314, spin and tracking bias signal 316, and laser controlsignal 318. Processor 302 also outputs reset signal 320 to reinitializeDSP 304. DSP 304 receives angular spin speed signal 312, laser powersignal 322, optical signals 324, mirror signal 326, track crossingsignal 328, and defect signal 308. Output signals from DSP 304 includefocus control signal 328, diagnostic signal 330, track control signal332, and write abort signal 334.

In one embodiment, mailbox 306 utilizes interrupts to interface with DSP304 and processor 302. In one implementation, a fixed number of mailboxinterrupts are available, and each mail box interrupt can be assigned tocommunicate a certain message. In other implementations, the messagecommunicated by a mailbox interrupt can vary, and a variable number ofmailbox interrupts can be available. (In another implementation, aninterrupt can be generated by the DSP 304 whenever it writes to one ofits mailbox registers.) FIGS. 3 a through 3 g show examples of mailboxmessages that can be communicated between processor 302 and DSP 304 viamailbox 306.

FIG. 3 a shows examples of messages in processor write/DSP read mailbox340 with sixteen slots for outgoing messages from processor 302 to DSP304. In one embodiment, these registers can be read or written by theprocessor 302, but they can only be read by the DSP 304. The first threemailbox messages are DSP control registers, as defined in FIGS. 3 bthrough 3 d. Each of the three control registers include sixteen bitsthat can be set or cleared to control focus, track, and seek functions,to provide signal and trace addresses, compensation parameters, andon/off switches for read/write components such as the laser. Examples ofother messages in mailbox 340 include acceleration parameters, offsetand shift values for focus and track gain parameters, sensor thresholddetection values, and crosstalk compensation.

FIG. 3 e shows examples of messages in processor read/DSP write mailbox342 with sixteen slots for messages from DSP 304 to processor 302. Themessages are used to convey information regarding focus, track, and seekerrors. In one embodiment, these registers can be read or written by theDSP 304 but they can only be read by the processor 302. Write mailbox342 includes one or more status registers with bits that can be set toconvey the status of focus, track, and seek operations as shown, forexample, in FIGS. 3 f and 3 g.

Note that other messages and registers can be included in addition to,or instead of, the messages and registers shown in FIGS. 3 a through 3g.

Referring now to FIG. 4, a diagram of one embodiment of code componentsincluded in processor 302 is shown. The code components represent setsof instructions that can be implemented in software, firmware, hardware,or a combination of software, firmware and hardware, as known in theart. In one embodiment, the components can include servo thread 404,real-time operating system (RTOS) 406, heartbeat interrupt 408, DSPstatus mailbox interrupt handler 410, spin control interrupts 412, andutility threads 414 that include read/write thread 416, asynchronousinput/output (async I/O) thread 418, diagnostic thread 420, timer thread422, interface thread 424, and file system manager 426.

Heartbeat interrupt 408 executes periodically at a variable rate, forexample, a rate of 20 Hz during sleep mode to a rate of 0.5 KHz duringexercise mode. The rates to be used for different modes can bedetermined based on the processing load, the frequencies associated withthe servo, and the processing capacity of processor 302. The heartbeatinterrupt 408 includes: a focus state machine to control the performanceof the focus servo such as closing and opening focus; a tracking statemachine to control the performance of the tracking servo such as turningtracking on/off and seeking; a spin state machine to control theperformance of the spin servo such as turning spin on and off; aphysical sector addresses (PSA) state machine to manage the reading ofphysical sector addresses; a performance monitoring state machine torequest a performance event or adjust drive parameters if poorperformance is detected; a power management state machine to transitionbetween the various power states of the drive; a monitor laser statemachine to coordinate the laser power with drive mode of operation; anadjust gains state machine to load the best focus and tracking gainsbased on the position of the actuator arm 104; and a load/eject statemachine to manage the loading and unloading of a cartridge containingoptical media 102.

DSP 304 issues messages that can include data and/or DSP statusinformation to mailbox 306. DSP status mailbox interrupt handler 410receives DSP status information and can request a notify event or atracking event to RTOS 406, as required. The data and status informationfrom mailbox 306 can be accessed by servo thread 404 and heartbeatinterrupt 408.

The command handler in servo thread 404 initiates actions for performingdifferent types of commands, including data transfer commands associatedwith reading from and writing to media 102 (FIG. 1 a), and diagnosticcommands for verifying the functionality of drive 100 (FIG. 1 a) duringengineering development, as well as during operation by a user. FIGS. 4a through 4 p show examples of data transfer and diagnostic commandsthat can be implemented in servo system 120 (FIG. 1 a). Diagnosticcommands can be included to control spin speed, test and calibratevarious components, open and close track and focus, turn variouscomponents on and off, set gain, offset, and compensation parameters,and error recovery. Data transfer commands can be included to seek, spinup, spin down, load/eject a media cartridge, and calibrate servo system120. The data transfer and diagnostic commands can include one or moreparameters, as shown in FIGS. 4 a through 4 p. Note that other commandscan be included in addition, or instead of, the commands shown in FIGS.4 a through 4 p.

The event handler in servo thread 404 facilitates communication betweencode components in processor 302. In one embodiment, real-time operatingsystem (RTOS) 406 issues servo events to the event handler. One servoevent is the notify event which can be issued to RTOS 406 by a servoperiodic heart beat interrupt 408 or the DSP status mailbox interrupthandler 410. A notify event issued by the DSP status mailbox interrupthandler 410 indicates that although no command is currently active, anerror has been detected that requires attention. A notify event can beissued by the heartbeat interrupt 408 to indicate whether a commandcould be completed.

As an example of how notify event requests issued by DSP status mailboxinterrupt handler 410 can be handled, assume drive 100 (FIG. 1 a) istracking and focus is closed when a shock, such as knocking drive 100,causes loss of focus. The DSP 304 includes code to compensate fortracking and focus errors, and to determine whether focus or trackinghave been lost. When the DSP 304 detects lost focus, one or more DSPstatus registers, such as Bit 5 in the DSP status register shown in FIG.3 f, in mailbox 306 are set accordingly. The mailbox 306 sends the DSPstatus message to DSP status mailbox interrupt handler 410, which issuesa request for a notify event to RTOS 406. The RTOS 406 issues a notifyevent to alert the servo thread 404. The event handler in servo thread404 then issues one or more commands to heartbeat interrupt 408 andmailbox 306 to take appropriate action, such as attempting to re-closefocus.

RTOS 406 can issue a command waiting event to indicate that a commandhas been issued to servo thread 404 to perform a drive function, such asspinning up the drive 100 (FIG. 1 a). Another event is a switches eventto indicate that the cartridge containing optical media 102 (FIG. 1 a)is being inserted or ejected from drive 100. RTOS 406 can also issuespin, focus, and tracking events to servo thread 404 in response torequests for spin, focus, and tracking events issued by their respectivestate machines in heartbeat interrupt component 408. Such event requestsare typically issued in response to completing, or failing to complete,a command.

As an example of how a spin, focus or tracking event can be handled,assume one of the utility threads 414 issues a servo command message tothe RTOS 406, and the RTOS 406 issues a command waiting event to theservo thread 404. The command handler in servo thread 404 subsequentlyissues a control command to the heartbeat interrupt 408. When theheartbeat interrupt 408 completes the command, it requests an eventcorresponding to the command, such as a spin, focus, or tracking event,from RTOS 406. The RTOS 406 generates the requested event and sends itto the servo thread 404. A servo command status is then sent from servothread 404 to the corresponding utility thread 414.

Heartbeat interrupt 408 also includes a recovery state machine. In oneimplementation, the recovery state machine advantageously enablescommands to be resumed where they left off after a problem has beendetected and corrected. For example, if a problem with closing focus isdetected while a read command is being processed, the recovery statemachine saves the current state of the drive 100 (FIG. 1 a), correctsthe focus problem, clears error indications, and restores the state ofdrive 100 to resume the read command where it left off.

In one embodiment, the functions performed by utility threads 414include the following: Spin Control Interrupts 412 measure the currentspindle speed, determine the correct spindle speed based on currenttrack position, and calculate the control signals to maintain a constantspeed or to change spindle speeds; Read/Write Thread 416 manages thereading of data from the disk and the writing of data to the disk; AsyncI/O Thread 418 is utilized primarily in engineering testing to managethe transfer of data from a user data input device, such as a keyboard,over an interface to the drive 100; Diagnostic Thread 420 executesdiagnostic commands, which are used primarily during engineeringtesting; Timer Thread 422 provides timing utilities used by the otherthreads; Interface Thread 424 manages the communication and datatransfer between the drive and the host; and File System 426 manages theorganization of data on the optical disc 102 (FIG. 1 a).

Servo Thread

Referring now to FIGS. 3, 4, and 5, an embodiment of main loop 500 inservo thread 404 is shown including an initialization path 502 and acontinuous path 504. Initialization path 502 includes process 506 toinitialize servo random access memory (RAM) variables, and process 508to initialize the frame rate of the heartbeat interrupt 408 based on aclock (not shown) in processor 302.

Processor 302 can include different power modes such as sleep mode (lowpower consumption), high power mode, and operating mode. In oneimplementation, processor 302 loads program code into DSP 304 every timepower is turned on in process 510 and then enters high power mode inprocess 512. In other embodiments, program code in DSP 304 can bepreloaded, and/or implemented in firmware or in hardware circuitry,eliminating the need for process 510.

Initialization path 502 can also include process 514 to initializeprocessing components associated with a spin motor driver for spin motor101 in servo system 120 (FIG. 1 a) as further described in The SpinMotor Servo System disclosures.

Initialization path 502 can also include processes 516, 518, and 520 toretrieve and load calibration values. Two or more different sets ofcalibration values may be available, including values that were setduring manufacture, values that were in use before the last power down,as well as updated values that are generated during power up.Alternatives for determining which set, or combination of sets, ofcalibration values to use are described in The Servo System Calibrationdisclosures.

Initialization path 502 can also include processes 524 and 526 toinitialize the actuator arm 104 (FIG. 1 a) to the center of the opticalmedia 102 (FIG. 1 a) and move the OPU 103 (FIG. 1 a) to a position awayfrom media 102. Process 528 places servo system 120 (FIG. 1 a) in aminimum power mode to conserve power while drive 100 is in idle mode.Process 530 enables heartbeat interrupt 408 and transfers control tocontinuous path 504.

In one embodiment, process 532 in continuous path 504 stays idle until anew event is received, such as a command event, a notify event due to anerror that has been detected, or a performance event due to a problemwith performing a command. In one implementation, process 532 canrelease processor 302 for use by other processing tasks until an eventis received.

When process 532 does receive an event, process 534 can increase theheartbeat rate. For example, if process 532 was waiting with a slow“resting” heartbeat rate of 20 Hz, the “exercise” heartbeat rate can beincreased to 0.5 KHz. Depending on whether a command event, a notifyevent, or a performance event was received, the RTOS 406 can issue theevent to servo thread 404 (FIG. 4), which subsequently invokes thecorresponding handler, i.e., command handler 536, event handler 538, orperformance event handler 540.

Once the actions associated with the event have been executed, process544 reduces the heartbeat rate and suspends execution of main loop 504by returning control to process 532 until another event is received.Servo thread 404 can release processor 302 when it is waiting for acommand or event, thereby preserving bandwidth of processor 302 for useby other components in drive 100 (FIG. 1 a).

Command Handler

FIG. 6 shows an example of processes that can be included in oneembodiment of command handler 536. Referring to FIGS. 4 and 6, duringeach pass of command handler 536, a command status and servo systemstatus message is sent to utility threads 414. The utility threads 414determine the actions to be performed, and transmit servo commandmessages to RTOS 406 as required, as indicated by process 602. RTOS 406issues a command waiting event to servo thread 404, which waits for theevent in process 604. When the command waiting event is received,process 606 sets a servo command active and a servo error state flag toindicate that a command is being processed.

The first pass through command handler 536, process 608 begins executingthe command in servo thread 404 by issuing a state machine controlmessage to the state machines in heartbeat interrupt 408. Heartbeatinterrupt 408 issues an event request to RTOS 406, and servo thread 404waits for the event from RTOS 406. Command handler 536 then determineswhich event was received in process 610. If the event was a spin, focus,or tracking event, process 612 checks the command status. If the commandwas completed with no errors, processes 614 and 616 clear the servoerror state flag and the servo command active flag, respectively, and acommand done event is requested from RTOS 406. RTOS 406 issues thecommand done event to the utility thread 414 that issued the commandmessage.

Referring again to process 610, if a notify or a time-out event isreceived while a command is being processed, process 620 initiatesrecovery for the notify event by transferring control to the recoverystate machine in heartbeat interrupt 408. The functions performed by therecovery state machine are described hereinbelow. The recovery statemachine issues event requests to communicate whether the recoveryattempt is complete, or whether it failed to RTOS 406.

RTOS 406 issues a recovery event indicating whether recovery completedor failed to servo thread 404. Servo thread 404 waits for either arecovery complete or recovery failed event and then transfers control toprocess 622. If recovery completed, process 622 transmits the recoverycomplete message to process 612. If the command was not completed afterrecovery, process 612 transfers control to process 624, which continuesexecuting the command that was being processed when the notify event wasreceived. Referring back to process 622, if the recovery process failed,process 628 sets the servo error state to indicate that the commandfailed, and process 616 clears the servo command active flag beforecontrol is transferred out of command handler 536.

Referring again to process 610, if a command abort event is received,process 626 replaces the command currently being processed with an abortcommand, and transfers control to process 624. The abort commandexecutes in the servo thread 404. One of the first actions performed isto turn the tracking servo off. Servo thread 404 changes the state ofthe tracking state machine executing in the heartbeat interrupt 408 andthen waits for a tracking event. The tracking state machine completes asequence of operations to open the tracking servo loop, as furtherdiscussed hereinbelow. When the tracking servo loop opens, the trackingstate machine requests the RTOS 406 to issue a tracking event. The RTOSgenerates the tracking event, which is received by the abort commandexecuting in the servo thread 404. After the tracking loop opens, theservo thread 404, heartbeat interrupt 408 and RTOS 406 coordinateefforts, in a fashion similar to that used to open the tracking loop, toopen the focus loop. Once the focus loop opens, the laser 218 (FIG. 2)is shut off. Next, the servo thread 404, heartbeat interrupt 408, andRTOS 406 again coordinate efforts to open the spin loop.

Event Handler

FIG. 7 shows an embodiment of event handler 538 that is executed byservo thread 404 when a notify event is received in process 702. In oneembodiment, requests for notify events are issued by heartbeat interrupt408 and mailbox interrupt 306 when a problem or error is detected. RTOS406 then issues the notify event to servo thread 404. In one embodiment,process 704 monitors the time between the notify events and the numberof notify events in order to avoid excessive recovery. The parametersfor determining when a recovery attempts become excessive can be setbased on a number of different criteria, such as number of recoveryattempts within a predetermined time period. For example, five recoveryattempts within five seconds can be considered excessive in oneembodiment, while other parameters and values can be used in otherembodiments.

If the recovery is not excessive, process 706 initiates recovery for thenotify event by transferring control to the recovery state machine inheartbeat interrupt 408. The functions performed by the recovery statemachine are described hereinbelow. The recovery state machine issuesevent requests to communicate whether the recovery attempt is complete,or whether it failed, to RTOS 406.

RTOS 406 issues a notify event indicating whether recovery completed orfailed to servo thread 404. Process 708 directs control based on whichevent is received. If recovery completed, the event handler is finished,and process 708 returns control to servo thread 404. If the recoveryattempt failed, process 708 transfers control to servo thread 404, whichprocesses an abort command. Note that the abort command in servo thread404 can also be executed if additional recovery would be excessive. Inone embodiment, servo thread 404 issues a state machine control messageto heartbeat interrupt 408. Heartbeat interrupt 408 requests the firstof a series events, such as a notify event, to RTOS 406. RTOS 406 issuesthe requested event to servo thread 404, and process 710 determineswhether the abort command processing is complete.

In one embodiment, processing an abort command includes heartbeatinterrupt 408 issuing a series of event requests including the notifyevent request described above, a spin event request, a focus eventrequest, and a tracking event request. The event requests are issued bythe state machines in heartbeat interrupt 408 when they finish tasksassociated with the abort command, such as turning off track, focus, andspin. The event requests can also be issued by DSP status mailboxinterrupt handler 410 when the DSP 304 detects a problem with theoperation of drive 100. Other event requests, such as turning off powerto the laser 218 (FIG. 2 b), can also be implemented. These eventrequests can be issued sequentially, or one or more events can be issuedsimultaneously, depending on the capability of RTOS 406 to process eventrequests in parallel or as a batch. For each event request, RTOS 406issues a corresponding event to servo thread 404. As each event, orgroup of events is received, process 710 determines whether the abortcommand processing is complete, or whether the time allowed to processthe abort command has been exceeded. When the abort command processingis complete, or the abort command times out before it is complete, theevent handler 538 is finished, and control returns to servo thread 404.

Performance Event Handler

FIG. 8 shows an embodiment of performance event handler 540 which isinvoked when a performance event is sent to servo thread 404 (FIG. 4). Aperformance event occurs when one of the state machines in heartbeatinterrupt 408 (FIG. 4) detect a problem or error that may be correctedby recalibrating drive 100 (FIG. 1 a). For example, if drive 100 (FIG. 1a) was initially powered on and calibrated indoors in an environmentwith a warm ambient temperature, and then used outside in a cold ambienttemperature, the calibration values being used may not be optimal forthe colder environment. Several different levels of recalibrationprocesses can be performed depending on the severity of the error,ranging from relatively low level of effort, to more complex processesrequiring greater effort.

FIG. 8 a shows one implementation of servo recalibration process 802that includes 6 different recalibration levels. Increased effort isundertaken to correct the detected error at each increasingrecalibration level. The recalibration processes are further describedin The Servo System Calibration disclosures. Switch 804 branches to thecurrent recalibration level. Level 0 performs servo engine and mediacalibration processes 806. If the error was not sufficiently correctedat level 0, level 1 performs notch calibration process 808 and thenperforms servo engine and media calibration processes 806 using the newvalues for the notch filter. Update flash process 810 is performed atthe end of both level 0 and level 1 recalibration to update currentcalibration values, or add another set of calibrations values that maybe factored in with another set of calibration values.

Level 2 recalibration includes performing focus offset jittercalibration process 812 to correct focus problems, followed by servoengine and media calibration processes 806. Level 3 performs trackingoffset jitter calibration process 814 to correct tracking errors,followed by servo engine and media calibration processes 806. Level 4performs adjust focus loop gain process 816, and level 5 performs adjusttracking loop gain process 818. Levels 4 and 5 can include adjusting thegain to achieve a particular crossover frequency. In one implementation,the loop gain is measured by injecting a fixed frequency and amplitudeinput signal into the closed loop and measuring the amplitude of theloop's response at the same frequency. The ratio of the loop's responseover the injected amplitude is the loop gain. This technique ofadjusting loop gain can affect the stability margins of drive 100 (FIG.1 a).

The servo engine calibration values include all values required tocalibrate drive 100. The media calibration values are a subset of theservo engine calibration values, which include only those parameterswhich vary as different pieces of media are inserted into the drive. Thecalibrated values include: OPU 103 (FIG. 1 a) offsets and gains, focusclosed threshold, focus sensor gain and offset, tracking sensor gain andoffset, focus loop gain, tracking loop gain, notch locations, sensorcrosstalk gain, focus sensor linearization, and tracking sensorlinearization. The media calibrations include: focus sensor gain andoffset, and tracking sensor gain and offset.

In one embodiment, the loop gain is measured by injecting a fixedfrequency and amplitude input signal into the closed loop and measuringthe amplitude of the loop's response at the same frequency. A digitalsummer is created in the DSP 304 to sum the input sinewave signal withthe output of a compensator. The output of the digital summer isconverted from a digital to an analog signal. The ratio of the output ofthe compensator over the output of the digital summer is the total openloop gain. This ratio should be 1.0 if the frequency of the disturbanceis at the desired crossover frequency and the gains are correct, asfurther described in The Servo System Calibration disclosures.

Referring again to FIG. 8, process 824 checks the value of a statusindicator returned by servo recalibration process 802. If thecalibration was successful, then process 826 monitors whether focusmisregistration (FMR), track misregistration (TMR), and read jitter arewithin predetermined limits. If FMR, TMR, and read jitter are withinlimits, then a status variable is set to indicate “no errors” in process828 and control is returned to servo thread 404 (FIG. 4). If FMR, TMR,and read jitter are not within limits, or if process 824 returns afailed status, then process 830 adjusts the recalibration level toincrease the effort to correct the problem. If all of the levelsavailable have not been attempted, then control transfers to process 802to perform the next level of recalibration. If all of the recalibrationlevels available have been attempted, then the status variable is set toindicate that an error is still present in process 832 and controltransfers back to servo thread 404.

Heartbeat Interrupt

Referring now to FIG. 9, a flow diagram of processes that can beincluded in heartbeat interrupt 408 is shown. In the embodiment shown,the time between heartbeat interrupts 408 is a variable that can be setand passed to heartbeat interrupt 408 according to a particularapplication or implementation of drive 100 (FIG. 1 a). In otherembodiments, the time allowed can be fixed to a particular value.Process 902 disables further interrupts so that the interrupt lastreceived from servo thread 404 (FIG. 4) can be processed. The interruptcounter is updated by a delta time value to create a timing clock usedby the state machines that are implemented in the heartbeat interrupt408. The delta time value can be set to any increment desired, such as avalue that corresponds to the rate of the heartbeat, in process 903.Process 904 reads the DSP status register, such as shown in FIG. 3 f, todetermine the status of the DSP 304 (FIG. 3).

In one embodiment, heartbeat interrupt 408 invokes a set of statemachines that manage various time-critical functions in heartbeatinterrupt 408. The embodiment shown in FIG. 9 includes power mode statemachine 910, recovery manager 912, tracking/seeking control statemachine 914, focus control state machine 916, spin control state machine918, monitor PSA state machine 920, laser control state machine 922,adjust gains state machine 924, performance monitor state machine 926,and monitor load/eject process 928. These processes are executed onceevery pass through heartbeat interrupt 408. Process 930 exits thecurrent interrupt and re-enables interrupts once the processes in theheartbeat interrupt 408 are complete.

In other implementations, other processes can be included to performfunctions in addition to, or instead of, the processes shown in FIG. 9.Further, one or more of the processes can be executed at different framerates relative to other processes.

Monitor Power Mode

Processor 302 (FIG. 3) can function in different power modes such assleep mode (low power consumption), high power mode, and operating mode.FIG. 10 shows one example of a state machine representing processesperformed by power mode state machine 910 that includes a requestdigital signal processor (DSP) only mode 1032, a request minimum powermode 1034, a request idle power mode 1036, and a request full power mode1038.

In the request DSP only mode 1032 and request minimum power mode 1034,process 1040 determines whether any loops are open or closed. A requestto change power modes can originate from the servo thread 404, theheartbeat interrupt 408 or any of the utility threads 414. Ideally, apower mode other than high power mode would not be requested while theservo tracking, focus or spindle loops are closed. Process 1040determines whether any servo loops are closed and coordinates openingthe loops before continuing to the requested power mode. Once all loopsare open, process 1042 disables the mailbox interrupt service routine,which is further described hereinbelow in the discussion of FIG. 21.

The power mode is then set to DSP only in the request DSP only mode1032, and to minimum power in the request minimum power mode 1034. Notethat process 1044 continues to monitor load/eject switches in theminimum power mode 1034. Process 1048 function which is called at theend of any interrupt. When the power mode reaches DSP_ONLY, MIN_POWER orIDLE_POWER, there is no need to execute all the state machines in theheartbeat interrupt 408. To bypass the execution of these statemachines, we use the K_OS_Intrp_Exit function to end the heartbeatinterrupt after executing the Monitor Power Mode state machine.

When the power state is minimum power (MIN POWER) mode, the power statecan transition to the idle mode. In the MIN POWER mode, the drive 100detects if a cartridge is present to be loaded or if a cartridge ejecthas been requested. The power mode transitions to the idle mode toperform the load or eject operation. The monitor load/eject process 928initiates the REQUEST IDLE process 1036. Process 1046 continues tomonitor load/eject switches in the idle power mode.

When full power is requested, the request full power mode 1038re-enables the mailbox interrupt routine and sets the power to full on.

Recovery

FIG. 11 shows an overview flow diagram of functions performed by oneembodiment of recovery manager 912 that can be implemented to recoverfrom problems with focus, tracking, or spin. The current drive state isstored in process 1104 based on parameters supplied by servo thread 404,heartbeat interrupt 408, and DSP status mailbox interrupt handler 410.This allows the state of the drive 100 (FIG. 1 a) to be restored toresume processing any commands at the point where they were interruptedwhen the problem was detected.

Process 1106 classifies the problem as a spin, focus, or trackingproblem based on error status information supplied by servo thread 404,heartbeat interrupt 408, and DSP status mailbox interrupt handler 410.Once the problem is classified, process 1108 finalizes the state to berestored, which may include determining the command that wasinterrupted, and storing the information where it can be accessed torestore the interrupted command.

Process 1110 performs clean up before attempting to recover from theproblem or error detected in process 1114. The steps performed duringthe cleanup process can vary depending on the state of the drive 100(FIG. 1 a) when the error was detected. Such clean up can include, forexample, managing laser power so that data is not written in anunintended location on the optical media 102 (FIG. 1 a).

When an “off disk” condition is detected, process 1112 biases thetracking actuator arm 104 (FIG. 1 a) back on to the optical media 102.If the actuator arm 104 does move back on to the optical media 102, thenprocess 1114 restores the previous drive state that was interrupted whenthe error was detected.

If process 1114 cannot recover from the tracking, focus or spin error,then failed recovery cleanup process 1116 is invoked to perform“cleanup” tasks, such as turning track and/or focus off, depending onthe problem. Process 1118 requests a RECOVERY_FAILED event from the RTOS406 (FIG. 4) to indicate that recovery was attempted, but not achieved.

If recovery was successful, process 1114 issues a notice that the drivestate was restored to process 1120, which then clears error bits inmailboxes 306 (FIG. 4) and requests a RECOVERY_COMPLETE event from theRTOS 406.

FIG. 11 a shows a recovery state machine 912′ that corresponds torecovery manager 912. FIG. 11 a shows states 1104′–1120′ that correspondto processes 1104–1120 in FIG. 11. The criteria shown above dashed linesin FIG. 11 a indicate the conditions required to transition to the nextstate, and the information below the dashed lines indicate the actiontaken upon transition.

In one embodiment, the following servo error states can be indicated bytrack, focus, and spin control processes:

-   -   Off Disk    -   Failed Auto Jump    -   Long Seek Failed    -   Failed Jump    -   Calibration Failure    -   Bad Spin    -   Bad Track    -   Bad Focus Caused Track    -   Bad Focus    -   Error Failed    -   Got Notify Event    -   Timed Out    -   Aborted

In one embodiment, the following recovery restore states can be saved:

-   -   Continue long seeks    -   Continue jumps    -   Reposition Current Track    -   Enable Auto Jumpback    -   Track On    -   Repeatable Run-Out (RRO) On    -   Constant Linear Velocity (CLV) Data    -   Spin On    -   Focus On

Off Disk Detection

Optical media 102 for drive 100 (FIG. 1 a) can be very small and it canbe difficult to prevent the OPU 103 from moving off the formatted areaof the optical media 102, such as at the innermost or outermostdiameter, where there are no tracks. FIGS. 12 a–12 c show an example ofan off disk detection process 1200 for detecting an off disk condition.FIG. 12 a shows a diagram of an embodiment of an off format detectionmanager that is executed as part of the classify problem state 1106′ inFIG. 11 a.

In FIG. 12 a, process 1202 includes detecting track crossings whenattempting to close tracking. If the DSP 304 (FIG. 3) does not detecttracking good or tracking bad within a predetermined time period, forexample, 500 milliseconds, in process 1204, an off-disk indication isset in process 1206. If the DSP 304 does detect a tracking goodcondition, process 1210 monitors the tracking control effort (TCE) todetermine whether an off disk condition exists.

FIG. 12 b shows a diagram of components utilized to perform off formatdetection for the off format detection manager shown in FIG. 12 a. FIG.12 b shows the relationship between the TCE signal and other componentsin drive 100, specifically, DSP tracking servo 1220 outputs the TCEsignal as a feedback signal to tracking/seeking state machine 914, aswell as to off disk detection process 1224. The TCE signal is based onthe track error signal. The TCE signal can be processed to indicate thelevel of effort being expended to achieve tracking. A method forgenerating the TCE signal is further disclosed in The Tracking andSeeking Servo System disclosures.

FIG. 12 c shows a diagram of logic to perform off format detection forthe off format detection manager shown in FIG. 12 a by determiningwhether the TCE signal indicates an off disk condition. Process 1230calculates the absolute value of the TCE signal. Process 1232 includesinputting the absolute value of the TCE signal to a filter, such as alow pass filter, to remove high frequency noise. In one embodiment, thecutoff frequency of the low pass filter is 10.6 Hertz, however othercutoff frequencies can be implemented according to the dynamics andfrequencies associated with drive 100.

Monitor Tracking/Seeking Servo

FIGS. 13 a–13 c show an embodiment of tracking/seeking control statemachine 914 represented by control state diagrams 1300, 1302, 1304 formonitoring and controlling track functions for drive 100 (FIG. 1 a).FIG. 13 a pertains to turning track on and off, FIG. 13 b pertains totrack jumps, and auto jumpback, and FIG. 3 c pertains to long seeks.

Referring now to FIG. 13 a, when a tracking turn on servo command isreceived while tracking acquisition state machine 1300 is in thetracking idle state 1306, tracking acquisition state machine 1300transitions to tracking turn on state 1308. If focus is not on, thentracking acquisition state machine 1300 enters tracking illegal state1310. If the drive has flash memory which contains valid calibrationvalues for operating over both premastered media and writeable media,the gain measure states 1380 and 1382 are used to determine whether theOPU 103 is currently over the premastered or the grooved areas, and toselect the values appropriate for the area of the media.

Before transitioning from track turn on state 1308 to gain measure state1380, a nominal TES gain and offset are programmed and the DSP 304 (FIG.3) is configured to measure the peak to peak amplitude of the TESsignal. Gain measure state 1380 enables the DSP 304 to begin to measurethe TES peak to peak amplitude and then transitions to gain measurestate 1382. Gain measure state 1382 allows the DSP 304 a predeterminedtime period, such as 25 milliseconds, to complete the TES peak to peakamplitude measurement. When the measurement is complete, a decisionregarding media area type is made based on the resultant amplitude. Arelatively small amplitude indicates that the OPU 103 is currently overpremastered media and the values appropriate for premastered media areloaded. A relatively large amplitude indicates that the OPU 103 iscurrently over an area of writeable media and the values appropriate forwriteable media are loaded. Also in gain measure state 1382, theWRITEABLEMEDIA bit (FIG. 3 d) of DSP Control Register 3 (FIG. 3 a) isset or cleared to tell the DSP 304 what type, or area, of media the OPU103 is over, as further described in The Tracking and Seeking ServoSystem disclosures. The tracking acquisition state machine 1300 thentransitions from state gain measure state 1382 to enable tracking state1384.

Referring back to track turn on state 1308, if the drive 100 does nothave valid calibration values stored in flash memory, then the gainmeasure states 1380 and 1382 are not used. Instead, the tracking statemachine 1300 transitions directly from track turn on state 1308 toenable tracking state 1384. In enable tracking state 1384, a trackingacquisition process in DSP 304 is invoked as further described in TheTracking and Seeking Servo System disclosures, and tracking waitacquisition state 1312 becomes active for a predetermined time delayperiod. When the delay period expires, a tracking integrator is enabledin the tracking acquisition process, and tracking wait integrator state1314 becomes active for a predetermined delay period. When the delayperiod expires, the state transitions to the tracking wait track errorsignal (TES) integrity state 1316 for another delay period beforeentering the tracking status state 1318.

If the tracking status is track_OK, the state transitions to and remainsin tracking active state 1320 until a problem with tracking is detected,at which point the state transitions to tracking turn off state 1322.The state then transitions through a series of tracking zero states1323–1324 to reset control flags and clear variables in the DSP 304(FIG. 3) associated with tracking before entering tracking off state1332.

While in the tracking active state 1320, a command to jump a singletrack or multiple tracks on optical media 102 (FIG. 1 a) can be issued.Track jumps can be implemented in a number of different ways includingjumping two or more at one time, jumping one track each revolution ofthe optical media 102, and jumping a specified multiple of tracks everyspecified number of revolutions of optical media 102. The jumps can bein the forward or reverse directions.

In one embodiment, laser power can be reduced to a low power mode from ahigh power mode while in the tracking active state 1320 during trackseeking functions. The laser power mode can also be reduced to the lowpower mode upon transition to the tracking turn off state 1322.

FIG. 13 b shows an example of a state chart that can be implemented tocontrol track jumps. When a single track jump command is received, thestate transitions from tracking active state 1320 to begin single jump1state 1332, where variables are set to indicate that it is not safe toread from or write to optical media 102 at this time. The state thentransitions to begin single jump2 state 1334, which issues a singletrack seek control command to DSP 304. When an auto jumpback command isreceived, the state transitions from tracking active state 1320 to beginauto jumpback state 1333, where variables can be set includingparameters to indicate the jump type, the number of tracks to jump, thedelay between track jumps, the number of revolutions (spin edge count)between jumps, the revolution counter (spin edge counter), and that itis not safe to read from or write to optical media 102 at this time. Thestate then transitions to sync auto jumpback state 1335, whichinitializes pertinent parameters and issues a single track seek controlcommand to DSP 304 once the pertinent spindle index occurs. If the PSAstate is not in PSA idle state 1602 (FIG. 16), then the PSA state is setto idle before entering the sync auto jumpback state 1335. The PSAstates are further described hereinbelow in the discussion of FIG. 16.

An adjust bias function 1337 can be preformed to provide the lowfrequency tracking control effort (TCE) and to allow the DSP 304 tohandle the high frequency TCE.

The state then transitions to track wait jump state 1336 afterrequesting the DSP 304 to start a single track seek, the reset jumpindicator is cleared, the indicators JUMP_P1_TRACK (to indicate a jumptoward the inside diameter of the media 102) and JUMP_M1_TRACK (toindicate a jump toward the outside diameter of the media 102) are set,the track count is set, the spin edge counter is cleared, and the spinedge count is set to the track jump count. The state remains in trackwait jump state 1336 until the DSP 304 returns a status indicator ofwhether or not the seek, also referred to as track jump(s), wassuccessful.

Some status indicators that are included in the embodiment shown in FIG.13 b include: bad track status, which causes a notify and tracking eventto be issued and transitions to track turn off state 1322; bad jump,which causes a transition to track bad jump state 1340; and good trackstatus, which causes a transition to track good jump 1342. Note that astate change in the mailbox 306 can also cause a transition to track badjump state 1340 or track good jump state 1342, as further explainedhereinbelow in the discussion of an embodiment of the mailbox interruptservice routine in FIG. 20 b.

The state transitions to track count jumps state 1344 aftercorresponding parameters are cleared and/or set from track bad jumpstate 1340 or track good jump state 1342. If more tracks are to bejumped, the state transitions to track jump settle state 1346, where thetransition to the track wait jump state 1336 is delayed for a specifiedtime period to allow the actuator arm 104 (FIG. 1 a) time to settlebefore the next jump. If no more tracks are to be jumped and the autojump back indicator is false, the state transitions back to trackingactive state 1320. If no more tracks are to be jumped and the auto jumpback indicator is true, the state transitions back to sync auto jumpbackstate 1335.

Referring now to FIG. 13 c, an embodiment of a state machine 1304 forcontrolling long seeks in response to receiving a seek command is shownbeginning with start long seek state 1350. Parameters Jump_Cnt_LoB,Jump_Cnt_MidB and Jump_Cnt_HiB represent the low, middle, and high bytesof the 24 bits used by the DSP 304 to determine the number of tracks toseek. The adjust bias seek function 1351 can be performed to generate abias value for the tracking actuator arm to provide the low frequencytracking control effort (TCE) and to allow the DSP 304 to handle thehigh frequency TCE. The bias before seek function 1353 can be performedto store the current tracking actuator arm bias value before a new valuefor this parameter is generated in the adjust bias seek function 1351.The stored value can be used when transitioning between states 1352 and1354.

Parameters such as a seek on flag, a track integrator on flag, a trackintegrator reset flag, a physical sector address (PSA) idle flag, andthe laser low power mode can be initialized before transitioning to longseek gain adjust state 1358. In the long seek gain adjust state 1358,the calibrated parameters appropriate for the type of media 102 expectedat the end of the seek are loaded. For example, if the OPU 103 isexpected to land on writeable media at the end of the seek, thecalibration parameters appropriate for writeable media are loaded inlong seek gain adjust state 1358. If the OPU 103 is expected to land onpremastered media at the end of the seek, the calibration parametersappropriate for premastered media are loaded in long seek adjust state1358.

The tracking control state machine 1304 then transitions to wait longseek state 1352. If the time allotted for a seek expires before the seekis completed, or the DSP 304 has set the BAD_SEEK bit (FIG. 3 g) of theDSP Status Register, the state transitions to failed long seek state1354. If the seek is completed, the state transitions to the long seekclear state 1356, where additional parameters can be cleared orre-initialized before transitioning to tracking wait integrator state1314.

FIG. 13 c also shows an example of a head load state machine 1390. Thepurpose of the head load state machine 1390 is to position the OPU 103over the area of the optical media 102 containing tracks to acquiretracking. The head load state machine 1390 can be used when the drive100 is in any physical orientation or in the presence of shock and/orvibration. Orientation and/or shock and vibration could cause OPU 103 tobe positioned off the portion of the optical media 102 containingtracks.

Head load state machine 1390 can commence in a begin head load onlystate 1360 or in a begin head load state 1362. If the head load statemachine 1390 begins in begin head load only state 1360, then the headload state machine 1390 will complete without beginning the trackingacquisition state machine 1300. This is accomplished by setting thefHeadLoadOnly flag to TRUE in begin head load only state 1360. If headload state machine 1390 begins in the begin head load state 1362, thenthe head load state machine 1390 will complete and then initiate thetracking acquisition state machine 1300. If the begin head load statemachine 1362 detects that the focus servo loop is not closed, or thetracking loop is closed, the state transitions track turn off state 1322where the process of shutting tracking off is initiated. In the beginhead load state 1362, if the focus servo is closed and the trackingservo is open, a bias voltage is applied to position the trackingactuator against an inside diameter (ID) crash stop in drive 100. Thebegin head load state 1362 also sets the spindle speed to apredetermined speed, such as 2930 RPM, and programs the DSP 304 tosample and report the TES signal. Begin head load state 1362 thentransitions to headload1 state 1366.

The headload1 state 1366 delays a predetermined time period, such as 30milliseconds, to allow the tracking actuator time to settle against theID crash stop and to give the DSP 304 time to complete the firstmeasurement. The state then transitions to headload2 state 1368 in whichmore TES samples are collected. When a total predetermined number ofsamples are collected, the state transitions to headload3 state 1370 inwhich the TES samples are used to determine if the OPU 103 is over theportion of the media 102 that includes tracks. If the OPU 103 is overthe track portion, the TES has a sinusoidal shape and many of thesampled points will be away from the average value of the sine wavecloser to the peak values. When off the track portion of the OPU 103,the TES signal is not sinusoidal and is roughly centered about anaverage value except where some feature exists in the media.Consequently, if the OPU 103 is not over the track portion, most of thesampled points will be relatively close to the average value of thecollected TES samples. This difference in the scatter of the TES samplesis used in the headload3 state 1370 to determine whether the OPU 103 isover the media 102. If headload3 state 1370 determines that the OPU 103is not over the media 102, the tracking bias is reduced, thus reducingthe force pushing the tracking actuator against the ID crash stop and atransition is made back to headload1 state 1362.

This process involving states 1366, 1368 and 1370 is repeated untilstate 1370 determines that the OPU 103 is over the track portion oruntil the bias forcing the tracking actuator against the ID crash stophas been reduced past a predetermined point that determines the headload state machine 1390 has failed. If the head load state machine 1390has failed, a transition is made from state 1370 to track turn off state1322. If headload3 state 1370 determines that the OPU 103 has beenpositioned over the track portion, the tracking bias is increased oneadditional step, in this embodiment 0×200 counts, and the statetransitions to headload4 state 1372. If the fHeadLoadOnly flag is TRUEafter a predetermined delay, such as 100 milliseconds, then a trackingevent is requested of the RTOS 406 and the state transitions to headload complete state 1376. If the fHeadLoadOnly flag is found to be FALSEafter a predetermined time delay, for example, 100 milliseconds, then atransition is made directly to the track turn on state 1308.

Monitor Focus Servo

FIGS. 14 a–14 c show an embodiment of focus control state machines 1400,1402, 1403, represented collectively by the focus control state machine916 shown in FIG. 9, for monitoring and controlling focus functions fordrive 100 (FIG. 1 a). FIG. 14 a pertains to acquiring focus, and turningfocus on and off, and FIGS. 14 b and 14 c pertain to determining a focusoffset for ramping the actuator arm 104 (FIG. 1 a) away from the opticalmedia 102 (FIG. 1 a).

Referring now to FIG. 14 a, when a focus servo command is received whilefocus control state machine 1400 is in the focus idle state 1406, focuscontrol state machine 1400 transitions to begin focus state 1408. If theactuator arm 104 (FIG. 1 a) is not ramped away from optical media 102(FIG. 1 a) then the state transitions through begin ramp away state 1408to focus ramp away state 1410. Control transitions between states 1410and 1412 until the profile to ramp the actuator away from the disk hasbeen completed.

Once the actuator arm 104 ramps away to the determined position, thestate transitions to begin focus acquire state 1414 if focus is to beturned on. The begin focus acquire state 1414 transitions to ramp focusacquire state 1416 where it provides a focus DAC value to ramp the focusactuator arm 104 towards the optical media until the DSP 304 returns astatus indicating whether or not focus closed. If the DSP 304 closedfocus, then focus control state machine 1400 transitions through focusloop closed state 1418, focus enable integrator state 1420, and focusenable focus error signal (FES) integrity state 1422, before enteringfocus active state 1424.

If the DSP 304 issues a focus_OK status after a predetermined delayperiod, then the state further transitions to focus active state 1428.If the DSP issues a focus_bad status and focus is not closed, then thestate transitions to focus push retry state 1426 and then to begin focusstate 1408 to re-attempt to acquire focus.

A method for acquiring and enabling focus that corresponds to states1414 through 1428, and FIG. 14 b, that can be utilized in DSP 304 isdescribed in The Tracking and Seeking Servo System disclosures.

Focus control state machine 1400 can transition to focus turn off state1430 under the following conditions: (1) current state is the ramp focusacquire state 1416 and the maximum ramp position was reached; (2)current state is focus push retry state 1426 and best push away value isgreater than or equal to nominal/4; or (3) a focus problem developswhile in focus active state 1428. The focus turn off state 1430transitions to the begin ramp away state 1408 and focus ramp away state1410. The “best push away value” represents the control effort used whenpositioning the actuator arm 104 away from the optical media 102. Anominal push away value can be used except in the retry efforts managedby focus push state 1426. In some situations, the actuator arm 104 canbecome stuck when the push away value is too large. If attempts atclosing focus are unsuccessful, focus push retry state 1426 is enteredusing nominal/2 as the best push away value. If attempts at closingfocus are still unsuccessful, a value of nominal/4 is used as the bestpush away value.

Referring to focus ramp away state 1410, if focus is to be turned off,then the state transitions through a series of zero focus states toclear focus parameters in DSP 304 before issuing a focus event andentering focus away state 1432. Otherwise, if focus is not to be turnedoff, the state transitions to begin focus acquire state 1414.

FIGS. 14 b and 14 c show embodiments of the focus control state machines1402, 1403 which can be used during calibration and engineering testing.States 1450 through 1454 in FIG. 14 b are used to move the actuator arm104 towards and away from the disk in a continuous sinusoidal motion.States 1456 through 1460 in FIG. 14 c follow a sinusoidal profile tomove the actuator arm 104 from one position to another position.

Monitor Spin Servo

FIG. 15 shows an example of a spin control state machine 918 that can beimplemented in heartbeat interrupt 408 (FIG. 4) to monitor the spinmotor 101 (FIG. 1 a) for optical media 102. Spin control state machine918 can be implemented along with the methods for controlling the spinmotor 101 as disclosed in The Spin Motor Servo System disclosures.During the start-up phase, spin control state machine 918 enters spinupinitialization align state 1502 and spinup align state 1504 in which arotor shaft in spin motor 101 is moved to a known state or position toensure that spin motor 101 is rotated in the proper direction.

When alignment is completed, the state transitions to spinup enableinterrupts state 1506 to initialize various parameters. The state thentransitions to spin up complete state 1508 and to spin final check state1510 to determine if the desired speed has been attained before anallotted spinup time period expires. If the spin motor 101 is spinningat the desired speed, the state transitions to spin constant linearvelocity (CLV) by track ID (also referred to as track number) state1512, where it remains until a spin problem is detected.

If the spin motor 101 did not spin up to the desired speed before thespinup time period expired, a spin event is issued, and the statetransitions to spin problem state 1514. Similarly, if a spin problem isdetected while in the spin CLV by track ID state 1512, a notify eventissues, and the state transitions to spin problem state 1514.

The spin problem state 1514 transitions to the spin turn off state 1516,and then to spin braking state 1518, where it remains for a specifiedtime period to stop the optical media 102 from spinning. A spin event isissued when the optical media 102 has stopped spinning, and the statethen transitions to and remains in spin off state 1520 until a newcommand to spin the media is received.

Monitor PSA

FIG. 16 shows an embodiment of a physical sector address (PSA) statemachine 920 in accordance with the present invention. One unique aspectof optical media 102 is that it can include a pitted PSA master areathat cannot be overwritten, and a grooved writeable area that can beoverwritten. PSA state machine 920 therefore can determine the positionof the actuator arm 104 (FIG. 1 a) in relation to the grooved and pittedareas whenever tracking is Active. It is not possible to read PSAsduring seeks or when tracking is not active.

If track or focus are off, PSA state machine 920 is put into the PSAidle state 1602 where no attempts to read PSAs are made. If the drive isboth focused and tracking, the PSA state machine 920 will try to reachPSA locked state 1608 where PSAs are successfully read. Each time thetracking/seeking state machine 914 (FIG. 9) reaches the TRACKING ACTIVEstate 1320 (FIG. 13 a), it will check if the PSA state is in PSA IDLEstate 1602. If so, the state transitions from PSA idle state 1602 to PSAenable state 1604. Upon transitioning from PSA idle state 1602 to PSAenable state 1604, the acquisition interrupts are disabled and flags areset to indicate that PSAs are not being read. Upon transitioning fromPSA enable state 1604 to PSA acquiring state 1606, PSA acquisition isenabled. If the PSAs can be read, the PSA state machine 920 transitionsto PSA locked state 1608. If the ability to read is not detected withina predetermined time period, such as 48 milliseconds, the PSA statemachine 920 transitions to PSA RETRY state 1610. PSA RETRY state 1610toggles between settings appropriate for pits and settings appropriatefor grooves. Once the settings have been changed, the PSA state machine920 begins the acquisition process again at PSA enable state 1604.

While in PSA locked state 1608, the most recently read PSA is monitored.If a new PSA is not read before the timeout period expires , the statetransitions to the PSA retry state 1610. Each time a new PSA is read,the value is compared to PSA_MAX to determine if the actuator arm 104 isclose to the last track on the optical media 102. PSA_MAX corresponds tothe last usable track on the optical media 102. If the actuator arm 104is determined to be close to the last track, then a predetermined numberof single track jumps, such as 40 single track jumps, are commanded tomove the tracking actuator arm 104 away from the edge of the opticalmedia 102. Alternatively, a multi-track seek function can be used tomove the tracking actuator arm 104 instead of multiple single trackjumps. The PSA IDLE state 1602 is then commanded. Each time the PSAlocked state 1608 does not have a new PSA, it predicts the current PSA.The predicted PSA is compared to PSA_MAX to determine if the actuatorarm 104 is close to the last track on the optical media 102. If theactuator arm 104 is determined to be close to the last track, then anumber of single track jumps are performed before transitioning to thePSA idle state 1602.

Monitor Laser

FIG. 17 shows an embodiment of a laser control state machine 922 inaccordance with the present invention. The state remains in laser offstate 1702 when a laser control variable indicates that power to thelaser in OPU 103 (FIG. 1) is off. The state transitions to laser onstate 1704 when power to the laser is turned on. When the optical media102 stops spinning, the state transitions back to laser off state 1702,and a laser control variable is set to OFF. In one implementation, aspin override variable can be used to allow the laser to be turned offeven if the optical media 102 is still spinning.

Adjust Gains

FIG. 18 shows an example of adjust gains state machine 924 in accordancewith the present invention. Adjust gains state machine 924 begins ingains idle state 1824, and transitions to gains adjust state 1826 whentracking is active. The gains are adjusted based on the current zone onoptical media 102 (FIG. 1 a) being accessed. In one implementation,optical media 102 can include sixteen different zones, and a zonecalibration tables can exist for each zone. The gains corresponding tothe particular zone being accessed are loaded while the state remains inthe gains adjust state 1826. The state remains in the gains adjust state1826 until tracking is turned off. A method for generating the zonecalibrations tables that can be utilized with adjust gains state machine924 is disclosed in The Servo System Calibration disclosures.

Monitor Performance

FIG. 19 shows an embodiment of a continuous performance monitor statemachine 926 in accordance with the present invention. In oneimplementation, performance monitor state machine 926 includes idlestate 1902, monitor initialization (init) state 1903, monitor focusmisregistration (FMR)/track misregistration (TMR) state 1904, andmonitor performance events state 1908. The state transitions from idlestate 1902 to monitor initialize state 1903 at the start ofinitialization, such as when drive 100 is powered on.

If focus and track are active, the state transitions to monitor FMR/TMRstate 1904. The track and focus error signals (TES and FES) are used togenerate FMR and TMR signals. If the FMR and/or TMR signals and/or readjitter values are out of predefined limits, then the state transitionsto performance event issued state 1908 to issue performance events basedon whether there is a problem with FMR, TMR, and/or read jitter.

Mailbox Interrupts

FIG. 20 a shows a flowchart of an embodiment of DSP status interruptlogic 2000 that can be included in DSP status mailbox interrupt handler410 (FIG. 4) in accordance with the present invention.

When the DSP status interrupt occurs, process 2002 disables furthernotification of interrupts from mailbox 306 (FIG. 4) to allow time toprocess the current DSP status interrupt. Process 2004 decodes the DSPstatus register to decode the message being sent by the DSP 304 (FIG.4). Examples of messages which can be sent by the DSP 304 are shown inFIGS. 3 f and 3 g. In one embodiment, the messages are implemented asstatus bit settings in one or more DSP control registers. Process 2004determines which of the status bits in the DSP control register(s) havechanged. Examples of bit settings to convey various messages in the DSPcontrol register(s) are shown in FIGS. 3 b, 3 c, and 3 d. Specificactions are taken in processes 2006 and 2008 based on which status bitthe DSP 304 has set. When the DSP status indicates a problem with theoperation of drive 100 (FIG. 1 a), process 2006 issues a request for anotify event, and a tracking, focus, or trace event, as requireddepending on the error condition, to RTOS 406 (FIG. 4). If the messagedecoded by process 2004 indicates an error condition, then process 2012records the servo error state that is used by heartbeat interrupt 408.Process 2008 changes focus and tracking state machine variables based onthe DSP status. At the end of the DSP status interrupt logic 2000,process 2010 re-enables the mailbox interrupt 306 so the DSP 304 cancontinue to send messages to the processor 302.

Referring now to FIGS. 20 a, 20 b, and 20 c, FIGS. 20 b and 20 c show anexample of logic included in processes 2004–2008, which is also referredto as the mailbox interrupt service routine (ISR) 2020. In FIG. 20 b,process 2022 decodes DSP status by determining which bits in the DSPstatus registers have changed from the previous pass through the mailboxISR 2020. Process 2024 then checks the TRACK_BAD and TRACK_BAD_SOURCEstatus variables. The status of the tracking jumps is then tested bydetermining whether GOOD JUMP or BAD JUMP indicators are set inprocesses 2026 and 2028. If one or both of the GOOD JUMP indicators isset, process 2030 determines if the tracking state is the track waitjump state 1336 (FIG. 13 b). If the tracking state is the track waitjump state 1336, then process 2032 changes the tracking state to thetrack good jump state 1342 (FIG. 13 b). If the BAD JUMP indicator isset, process 2034 determines if the tracking state is the track waitjump state 1336 (FIG. 13 b). If the tracking state is the track waitjump state 1336, then process 2036 changes the tracking state to thetrack bad jump state 1340 (FIG. 13 b).

Process 2038 determines whether the FOCUS_BAD indicator is set. If so,process 2040 determines if the focus state is in the focus active state1428 (FIG. 14 a). If so, then process 2042 updates the servo error stateindicator to indicate bad focus, process 2044 requests a notify eventfrom RTOS 406, process 2046 sets the focus state to focus turn off state1430, and process 2048 determines whether auto jump back is enabled. Ifauto jump back is enabled, process 2050 update the servo error status toindicate a failure during autojump, otherwise, process 2052 determineswhether the tracking state is in the track off state 1332 (FIG. 13 a).

If the tracking state is not in the track off state 1332, then process2054 determines whether the tracking state is in the wait long seekstate 1352 (FIG. 13 c). If so, process 2056 updates the servo errorstatus to indicate a failure during long seek. Process 2058 then setsthe tracking state to the track turn off state 1322, whether or not thetracking state was the wait long seek state 1352 in process 2054.Process 2060 updates the servo error status to indicate that thetracking problem was caused by loss of focus.

Process 2062 determines whether the focus state is in the focus loopclosed state 1418 (FIG. 14 a). If so, then process 2064 determineswhether the DSP status indicates that ramp focus has been acquired. Ifso, then process 2066 sets the focus state to the focus loop closedstate 1418.

In FIG. 20 c, process 2064 decodes DSP status by determining which bitsin the DSP status registers have changed from the previous pass throughthe mailbox ISR 2020. Process 2066 then checks the TRACK_BAD statusvariable. If TRACK_BAD is set, process 2068 determines if the trackingstate is in the process of closing tracking. If not, process 2069determines whether tracking is active. If tracking is active, thenprocess 2070 updates the servo error state to BAD_TRACK, process 2071requests a notify event from RTOS 406, and process 2072 sets the trackstate to the track turn off state.

Referring again to process 2069, if tracking is not active, process 2073determines whether a jump (seek) is in progress. If a jump is inprogress, process 2074 updates the servo error state to BAD_TRACK,FAILED_JUMP. Process 2075 then determines whether the tracking state isin the auto jump back state. If not, then process 2076 determineswhether a command is active. If so, process 2077 issues a trackingevent. If process 2076 determines that a command is not active, thenprocess 2079 issues a notify event.

Referring again to process 2075, if the tracking state is in the autojump back state, then process 2078 updates the servo error state toFAILED_AUTOJUMP, and process 2079 issues a notify event.

Referring again to process 2073, if a jump is not in progress, process2080 determines whether a long seek is in progress. If so, then the DSPstatus is set to indicate LONG_SEEK_FAILED in process 2081 and process2077 issues a tracking event.

Process 2072 sets the track state to the track turn off state afterprocesses 2077 and 2079 are finished, or if process 2080 determined thatthe track state was not the long seek state.

Process 2082 then determines if any other bits in the DSP statusregisters have changed from the previous pass through the mailbox ISR2020. Process 2083 checks the TRACK_BAD_SOURCE status variable is set.If TRACK_BAD_SOURCE is set, process 2084 determines if the trackingstate is in the process of closing tracking. If not, process 2085determines whether tracking is active. If tracking is active, thenprocess 2086 updates the servo error state toBAD_FOCUS_CAUSED_BAD_TRACK, process 2087 requests a notify event fromRTOS 406, and process 2088 sets the track state to the track turn offstate.

Referring again to process 2085, if tracking is not active, process 2089determines whether a jump (seek) is in progress. If a jump is inprogress, process 2090 updates the servo error state to BAD_TRACK,FAILED_JUMP. Process 2091 then determines whether the tracking state isin the auto jump back state. If not, then process 2092 determineswhether a command is active. If so, process 2093 issues a trackingevent. If process 2092 determines that a command is not active, thenprocess 2095 issues a notify event.

Referring again to process 2091, if the tracking state is in the autojump back state, then process 2094 updates the servo error state toFAILED_AUTOJUMP, and process 2095 issues a notify event.

Referring again to process 2089, if a jump is not in progress, process2096 determines whether a long seek is in progress. If so, then the DSPstatus is set to indicate LONG_SEEK_FAILED in process 2097 and process2093 issues a tracking event.

Process 2088 sets the track state to the track turn off state afterprocesses 2093 and 2095 are finished, or if process 2096 determined thatthe track state was not the long seek state.

The various embodiments and implementations of the servo control systemdescribed herein thus address the combination of servo system designchallenges. The servo control system architecture includes uniquemethods of sharing a general purpose processor between the servo systemand the other drive systems, unique methods of using a dedicated highspeed processor for time critical servo functions, unique methods forcommunicating between the dedicated servo processor and the sharedgeneral purpose processor, unique methods of distributing the servoprocessing between the general purpose processor and the dedicated servoprocessor, and unique methods of distributing the servo processingwithin the general purpose processor between a main loop servo threadprocess and a background periodic heartbeat interrupt process.

The architecture addresses problems with performing operations on mediahaving a small form factor, such as the need for periodic recalibration,compensation for the flexible focus and tracking actuators, nonlinearand crosscoupled tracking and focus position sensors, dynamiccrosscoupling between the multiple servo loops, need for low power toconserve battery life, removable and interchangeable media, need tohandle media defects exacerbated by the first surface recording,presence of both premastered and user writeable areas on the same disk,need to operate in wide range of conditions including any physicalorientation, wide range of temperatures and humidity, and the presenceof shock and vibration.

Embodiments of the present invention can be implemented to function onone or more computer processors, however those skilled in the art willappreciate that certain aspects of various embodiments can bedistributed as a program product in a variety of forms, and that thepresent invention applies equally regardless of the particular type ofsignal bearing media used to actually carry out the distribution.Examples of signal bearing media include: writeable type media such asfloppy disks and CD-ROM, transmission type media such as digital andanalog communications links, as well as media storage and distributionsystems developed in the future.

The foregoing detailed description has set forth various embodiments ofthe present invention via the use of block diagrams, flowcharts, andexamples. It will be understood by those within the art that each blockdiagram component, flowchart step, and operations and/or componentsillustrated by the use of examples can be implemented, individuallyand/or collectively, by a wide range of hardware, software, firmware, orany combination thereof.

The above description is intended to be illustrative of the inventionand should not be taken to be limiting. Other embodiments within thescope of the present invention are possible. Those skilled in the artwill readily implement the steps necessary to provide the structures andthe methods disclosed herein, and will understand that the processparameters and sequence of steps are given by way of example only andcan be varied to achieve the desired structure as well as modificationsthat are within the scope of the invention. Variations and modificationsof the embodiments disclosed herein can be made based on the descriptionset forth herein, without departing from the spirit and scope of theinvention as set forth in the following claims.

1. An apparatus for controlling tracking and seeking in an optical discdrive for optical media with a pitted premastered area that cannot beoverwritten and a grooved user-writeable area that can be overwritten,comprising: an optical pick-up unit; an analog-to-digital convertercoupled to receive signals from detectors in the optical pick-up unitand provide digital signals; a digital signal processor coupled toreceive the digital signals and calculate a tracking error signal, thedigital signal processor calculating a control signal for driving aservo system to reduce the calculated tracking error signal; the servosystem including: means for turning tracking on and off; and means forjumping tracks on the optical media.
 2. The apparatus, as set forth inclaim 1, further comprising means for transitioning from a tracking idlestate to a tracking turn on state when a tracking turn on servo commandis received.
 3. The apparatus, as set forth in claim 1, furthercomprising means for entering a tracking illegal state if focus is notactive.
 4. The apparatus, as set forth in claim 1, further comprisingmeans for selecting gain and calibration values based on whether theoptical pickup unit is over the premastered or the writeable areas ofthe optical media.
 5. The apparatus, as set forth in claim 1, furthercomprising means for determining whether the optical pickup unit is overthe premastered or the writeable areas of the optical media.
 6. Theapparatus, as set forth in claim 1, wherein the means for determiningwhether the optical pickup unit is over the premastered or the writeableareas of the optical media comprises means for measuring the peak topeak amplitude of the tracking error signal.
 7. The apparatus, as setforth in claim 1, further comprising means for delaying transition to atracking active state to allow time for control system parameters to beinitialized.
 8. The apparatus, as set forth in claim 1, furthercomprising means for jumping a single track on the optical media.
 9. Theapparatus, as set forth in claim 1, wherein the means for jumping trackson the optical media includes at least one of: means for jumpingmultiple tacks on the optical media; means for jumping a single track onthe optical media; means for jumping a specified number of tracks everyspecified number of revolutions of the optical media; and means forjumping in forward or reverse directions.
 10. The apparatus, as setforth in claim 1, further comprising means for disabling reading fromand writing to the optical media while jumping tracks.
 11. Theapparatus, as set forth in claim 1, further comprising means forperforming an auto jumpback function.
 12. The apparatus, as set forth inclaim 11, wherein parameters for controlling jumps include at least oneof: jump type, number of tracks to jump, time delay between track jumps,number of revolutions of the optical media between jumps, and whether itis not safe to read from or write to the optical media.
 13. Theapparatus, as set forth in claim 11, further comprising means forgenerating a bias value for a tracking arm actuator, wherein the biasvalue can be used to provide a low frequency tracking control effort(TCE) and to handle high frequency TCE.
 14. The apparatus, as set forthin claim 1, further comprising means for generating a status indicatorof whether a track jump was successful, wherein the status indicates atleast one of: bad track, bad jump, good track, and good jump.
 15. Theapparatus, as set forth in claim 1, further comprising means forperforming long seeks.
 16. The apparatus, as set forth in claim 15,further comprising means for predicting whether a tracking actuator armwill be positioned over the premastered area or the writeable area atthe end of the long seek, and loading calibration parameterscorresponding to the type of media over which the tracking actuator armwill be positioned at the end of the long seek.
 17. The apparatus, asset forth in claim 15, further comprising means for waiting until a timeperiod allotted for performing the long seek expires, and to set a badseek indicator to indicate whether the long seek failed or completed.18. The apparatus, as set forth in claim 1, further comprising means forpositioning the optical pickup unit over an area of the optical mediacontaining tracks to be acquired.
 19. A method for controlling trackingand seeking in an optical disc drive for optical media with a pittedpremastered area that cannot be overwritten and a grooved user-writeablearea that can be overwritten, comprising: receiving digitized opticalpickup unit signals; within a digital signal processor, forming atracking error signal from the digitized optical pickup unit signals;turning tracking on and off; and jumping tracks on the optical media.20. The method, as set forth in claim 19, further comprisingtransitioning from a tracking idle state to a tracking turn on statewhen a tracking turn on servo command is received.
 21. The method, asset forth in claim 19, further comprising entering a tracking illegalstate if focus is not active.
 22. The method, as set forth in claim 19,further comprising selecting gain and calibration values based onwhether an optical pickup unit is over the premastered or the writeableareas of the optical media.
 23. The method, as set forth in claim 19,further comprising determining whether an optical pickup unit is overthe premastered or the writeable areas of the optical media.
 24. Themethod, as set forth in claim 19, wherein the determining whether theoptical pickup unit is over the premastered or the writeable areas ofthe optical media comprises measuring the peak to peak amplitude of atracking error signal.
 25. The method, as set forth in claim 19, furthercomprising delaying transition to a tracking active state to allow timefor control system parameters to be initialized.
 26. The method, as setforth in claim 19, further comprising jumping a single track on theoptical media.
 27. The method, as set forth in claim 19, wherein thejumping tracks on the optical media includes at least one of: jumpingmultiple tracks on the optical media; jumping a single track on theoptical media; jumping a specified number of tracks every specifiednumber of revolutions of the optical media; and jumping in forward orreverse directions.
 28. The method, as set forth in claim 19, furthercomprising disabling reading from and writing to the optical media whilejumping tracks.
 29. The method, as set forth in claim 19, furthercomprising performing an auto jumpback function.
 30. The method, as setforth in claim 29, wherein parameters for controlling jumps include atleast one of: jump type, number of tracks to jump, time delay betweentrack jumps, number of revolutions of the optical media between jumps,and whether it is not safe to read from or write to the optical media.31. The method, as set forth in claim 29, further comprising generatinga bias value for a tracking arm actuator, wherein the bias value can beused to provide a low frequency tracking control effort (TCE) and tohandle high frequency TCE.
 32. The method, as set forth in claim 19,further comprising generating a status indicator of whether a track jumpwas successful, wherein the status indicates at least one of: bad track,bad jump, good track, and good jump.
 33. The method, as set forth inclaim 19, further comprising performing long seeks.
 34. The method, asset forth in claim 33, further comprising predicting whether a trackingactuator arm will be positioned over the premastered area or thewriteable area at the end of the long seek, and loading calibrationparameters corresponding to the type of media over which the trackingactuator arm will be positioned at the end of the long seek.
 35. Themethod, as set forth in claim 33, further comprising waiting until atime period allotted for performing the long seek expires, and to set abad seek indicator to indicate whether the long seek filed or completed.36. The method, as set forth in claim 19, further comprising positioningan optical pickup unit over an area of the optical media containingtracks to be acquired.